1. Field of the Invention
The invention generally relates to a pulse width modulation (PWM) controller for an inverter, and more particularly, relates to a PWM controller that provides variable gain control in a voltage regulation loop to regulate an output voltage of the inverter.
2. Description of the Related Art
An inverter (or DC-to-AC conversion circuit) is typically used to drive a fluorescent lamp. The inverter can vary its frequency or PWM duty cycle to generate an increasing output voltage (or open lamp output voltage) with a sufficient voltage level to strike an unlit fluorescent lamp. The output voltage is sensed to generate a feedback voltage for a voltage regulation loop of the inverter. The inverter generally starts to regulate the output voltage when the feedback voltage reaches the level of an internal reference voltage corresponding to a desired level for the regulated output voltage. The output voltage can easily overshoot before reaching a stable regulation point due to feedback delay.